JPWO2017145248A1 - COMMUNICATION DEVICE, COMMUNICATION METHOD, AND COMMUNICATION PROGRAM - Google Patents

Abstract

The MAC control unit (404) determines an initial transmission waiting time, which is a waiting time before the initial transmission of data, using a random number from the first time width. In addition, when the initial transmission fails, the MAC control unit (404) sets a retransmission waiting time, which is a waiting time before performing data retransmission, in a second time width shorter than the first time width. To determine using a random number.

Description

The present invention relates to a technique for controlling a waiting time provided before data transmission.
In the following, control of waiting time in wireless communication will be mainly described.

In wireless communication standards represented by IEEE802.11 and IEEE802.15.4, CSMA / CA (Carrier Sense Multiple Access Collision Aviation) is adopted as a communication procedure for wireless communication. In the CSMA / CA system, a random time waiting time is set before transmitting a radio frame, and the radio frame is transmitted after the waiting time expires. When a failure in transmitting the radio frame is detected, the waiting time is set again, and the wireless frame is transmitted again after the waiting time has expired.
In IEEE802.15.4, the waiting time for retransmission is reset within the range of “minimum setting value to maximum setting value” of the back-off timer (IEEE Std 802.15.4). In IEEE 802.11, a backoff timer is extended for each retransmission by a binary exponential backoff (BEB) method, thereby increasing the probability of collision avoidance with the surroundings (IEEE Std 802. 11).

N-BEB: New backoff algorithm for IEEE 802.11 MAC protocol <http: // ieexplore. iee. org / xpl / login. jsp? tp = & arnumber = 6895627 & url = http% 3A% 2F% 2Fieexplore. iee. org% 2Fxpls% 2Fabs_all. jsp% 3Farnumber% 3D6895627> IEEE 802.15.4 <https: // standards. iee. org / geteeee802 / download / 802.15.4-2011. pdf>

  For urgent messages such as alarm notifications from alarm devices, it is required to shorten the time until transmission. However, in an environment where nodes are dense, wireless communication collisions are likely to occur. In an environment where radio communication collisions are likely to occur, the initial transmission is likely to fail, and if the initial transmission fails, retransmission is performed after waiting for a waiting time for retransmission. In IEEE802.15.4, retransmission requires a waiting time equivalent to the initial transmission. In addition, in the IEEE 802.11 BEB method, the waiting time for retransmission increases with each retransmission.

  As described above, in the conventional technology, the initial transmission is likely to fail in an environment where radio communication frequently occurs or a situation where alarm notifications are simultaneously generated from multiple nodes. There is a problem that data transmission is not completed within the required time.

  The main object of the present invention is to solve such a problem, so that even if the initial transmission fails, retransmission can be performed early so that data transmission can be completed within the required time. The main purpose is to do.

The communication device according to the present invention is
An initial transmission waiting time determination unit for determining an initial transmission waiting time, which is a waiting time before performing the first transmission of data, using a random number from the first time width;
When the first transmission fails, a retransmission waiting time that is a waiting time before performing data retransmission is determined from the second time width shorter than the first time width using the random number. A retransmission waiting time determination unit.

  According to the present invention, since the retransmission waiting time is selected from the second time width shorter than the first time width, it is possible to increase the possibility that the retransmission is performed early even if the initial transmission fails. be able to.

1 is a diagram illustrating a configuration example of a wireless communication system according to a first embodiment. FIG. 6 shows another configuration example of the wireless communication system according to the first embodiment. FIG. 3 is a diagram illustrating a hardware configuration example of the wireless communication apparatus according to the first embodiment. 3 is a diagram illustrating an example of a functional configuration of a wireless communication apparatus according to Embodiment 1. FIG. FIG. 3 is a flowchart showing an operation example of the wireless communication apparatus according to the first embodiment. FIG. 3 is a flowchart showing an operation example of the wireless communication apparatus according to the first embodiment. FIG. 3 is a flowchart showing an operation example of the wireless communication apparatus according to the first embodiment. FIG. 3 is a flowchart showing an operation example of the wireless communication apparatus according to the first embodiment. FIG. 4 is a diagram illustrating an operation example of a MAC control unit according to the first embodiment. FIG. 4 is a diagram illustrating an operation example of a MAC control unit according to the first embodiment. The figure which shows the example of the initial transmission waiting time and retransmission waiting time concerning Embodiment 1. FIG. The figure which shows the example of the initial transmission waiting time and retransmission waiting time concerning Embodiment 1. FIG. The figure which shows the example of the initial transmission waiting time and retransmission waiting time which concern on Embodiment 3. FIG. FIG. 10 is a diagram illustrating an operation example of a MAC control unit according to the fourth embodiment.

Embodiment 1 FIG.
*** Explanation of configuration ***
FIG. 1 shows a configuration example of a radio communication system according to the present embodiment.
The wireless communication system shown in FIG. 1 includes a GW (gateway) device 200 and a plurality of wireless communication devices 101 to 105.
Each of the wireless communication devices 101 to 105 transmits data to the GW device 200 by wireless communication.
Note that when there is no need to distinguish each of the wireless communication devices 101 to 105, the wireless communication devices 101 to 105 are collectively referred to as the wireless communication device 100.

FIG. 2 shows a configuration example of the radio communication system according to the present embodiment.
The wireless communication system illustrated in FIG. 2 includes a GW apparatus 200 and a plurality of wireless communication apparatuses 110 to 151.
The wireless communication devices 110, 120, 130, 140, and 150 can directly perform wireless communication with the GW device 200.
On the other hand, the wireless communication devices 111, 131, 132, and 151 cannot directly perform wireless communication with the GW device 200, and in order to transmit data to the GW device 200, relaying by another wireless communication device is necessary. It is.
Specifically, the wireless communication device 111 transmits data to the GW device 200 via the wireless communication device 110.
In addition, the wireless communication devices 131 and 132 transmit data to the GW device 200 via the wireless communication device 130.
Further, the wireless communication device 151 transmits data to the GW device 200 via the wireless communication device 150.
Also in the wireless communication system of FIG. 2, when it is not necessary to distinguish each of the wireless communication devices 110 to 151, the wireless communication devices 110 to 151 are collectively referred to as the wireless communication device 100.

  FIG. 3 shows a hardware configuration example of the wireless communication apparatus 100 according to the present embodiment. FIG. 4 shows a functional configuration example of radio communication apparatus 100 according to the present embodiment.

As shown in FIG. 3, the wireless communication device 100 is a computer including a wireless interface 301, a wireless MAC processing processor 302, a sensor interface 303, a processor 304, a ROM (Read Only Memory) 305, and a RAM (Random Access Memory) 306. .
The wireless interface 301 is a circuit that serves as an interface with a wireless communication line. The wireless interface 301 implements the sensor interface control unit 401 shown in FIG.
The sensor interface 303 is a circuit that serves as an interface with the sensor. The sensor interface 303 receives a signal notifying a phenomenon detected by the sensor (hereinafter referred to as a sensor signal). The sensor detects a phenomenon that is a target of the emergency notification and a phenomenon that is not a target of the emergency notification. When the sensor detects a phenomenon to be an emergency notification target, the wireless communication device 100 needs to notify the notification destination device of the phenomenon as an emergency notification. On the other hand, when the sensor detects a phenomenon that is not an emergency notification target, the wireless communication device 100 notifies the notification destination device of the phenomenon as a normal application notification. The phenomenon subject to emergency notification is, for example, an earthquake or a fire. Further, for example, the fact that an alarm is output by a device in the factory may be included in the phenomenon that is the subject of the emergency notification. The notification destination apparatus is the GW apparatus 200 in the case of the wireless communication apparatus 101 in FIG. 1, and the wireless communication apparatus 110 in the case of the wireless communication apparatus 111 in FIG.
The wireless MAC processor 302 is a processor that executes the MAC controller 404 shown in FIG.
The processor 304 is a processor that executes the application determination unit 402 and the priority control unit 403 illustrated in FIG.
The wireless MAC processing processor 302 and the processor 304 are, for example, a CPU (Central Processing Unit). The wireless MAC processing processor 302 and the processor 304 may be different CPUs or the same CPU.
The application determination unit 402, the priority control unit 403, and the MAC control unit 404 illustrated in FIG. 4 are realized by a program. Programs that implement the application determination unit 402, the priority control unit 403, and the MAC control unit 404 are stored in the ROM 305, loaded into the RAM 306, and executed by the wireless MAC processing processor 302 and the processor 304.
In addition to the above programs, the ROM 305 stores control information and setting information necessary for controlling the wireless communication apparatus 100.
The RAM 306 constitutes the data management unit 405 shown in FIG.

  In FIG. 4, a sensor interface control unit 401 controls the sensor interface 303 of FIG.

When the sensor interface 303 receives a sensor signal, the application determination unit 402 determines whether or not the phenomenon notified by the sensor signal is a phenomenon that is a target of an emergency notification.
Hereinafter, the reception of the sensor signal by the sensor interface 303 is also referred to as the occurrence of a transmission event. In the following, the case where the phenomenon that is the subject of the emergency notification is notified in the sensor signal is also referred to as the occurrence of an emergency event.

  The priority control unit 403 sets a priority for the sensor signal. Specifically, the priority control unit 403 sets a high priority for the sensor signal for which the emergency notification is performed, and sets a priority lower than the priority for the emergency notification for the sensor notification for which the normal application notification is performed. .

The MAC control unit 404 generates a radio frame that is data including a sensor signal, and determines a waiting time before transmitting the radio frame.
More specifically, the MAC control unit 404 determines an initial transmission waiting time, which is a waiting time before performing the initial transmission of the radio frame, using a random number from the first time width. In addition, when the initial transmission fails, the MAC control unit 404 sets a retransmission waiting time, which is a waiting time before performing retransmission of the radio frame, from the second time width shorter than the first time width. Determine using random numbers. The case where the initial transmission fails is a case where the initial transmission cannot be performed by CCA (Clear Channel Attachment) or a case where the initial transmission can be performed but a response to the initial transmission cannot be received.
Further, the MAC control unit 404 determines an initial transmission waiting time for each priority set by the priority control unit 403, and determines a retransmission waiting time for each priority set by the priority control unit 403.
The MAC control unit 404 sets the determined initial transmission waiting time or retransmission waiting time in the back-off timer. When the back-off timer expires (when the initial transmission waiting time or retransmission waiting time expires), the wireless frame is output to the wireless interface control unit 406.
Note that the MAC control unit 404 corresponds to an initial transmission waiting time determining unit and a retransmission waiting time determining unit. The operations performed by the MAC control unit 404 correspond to initial transmission wait time determination processing and retransmission wait time determination processing.

  The data management unit 405 stores the address of the notification destination device.

  The wireless interface control unit 406 transmits the wireless frame generated by the MAC control unit 404 to the notification destination apparatus as an emergency notification or a normal application notification.

*** Explanation of operation ***
Next, an outline of the operation of radio communication apparatus 100 according to the present embodiment will be described. Note that the operation of the wireless communication apparatus 100 described below is an example of a communication method and a communication program.

First, the sensor interface control unit 401 receives a sensor signal from a sensor.
Next, the application determination unit 402 analyzes the type of the sensor signal received by the sensor interface control unit 401 and determines a phenomenon notified by the sensor signal. Specifically, a table in which the type (identifier) of the sensor signal is associated with the phenomenon notified by the sensor signal is held in the ROM 305, and the application determination unit 402 refers to the table and uses the sensor signal. Determine the phenomenon being notified. Furthermore, the application determination unit 402 determines whether or not the phenomenon notified by the sensor signal is an emergency notification target. Specifically, a table describing whether or not each event is subject to emergency notification is held in the ROM 305, and the application determination unit 402 refers to the table and is notified by a sensor signal. It is determined whether or not is subject to emergency notification.
Next, the application determination unit 402 outputs a sensor signal and information indicating whether or not the phenomenon notified by the sensor signal is an emergency notification target to the priority control unit 403.
The priority control unit 403 sets a priority for the sensor signal. That is, the priority control unit 403 sets a high priority or a highest priority for the sensor signal when the phenomenon notified by the sensor signal is a target of an emergency notification. On the other hand, when the phenomenon notified by the sensor signal is the target of the normal application notification, the priority control unit 403 sets the normal priority or the low priority for the sensor signal. As described above, the priority control unit 403 sets a higher priority for the emergency notification than for the normal application notification.
The priority control unit 403 outputs the sensor signal and information indicating the priority set for the sensor signal to the MAC control unit 404.

Next, the MAC control unit 404 generates a wireless frame that is data including a sensor signal, stores the generated wireless frame in a queue for initial transmission for each priority, and waits for initial transmission using a random number. The time is determined, and the determined initial transmission waiting time is set in the initial transmission back-off timer.
For example, in the case of a high priority sensor signal, the MAC control unit 404 stores the wireless frame in a high priority initial transmission queue, and determines a high priority initial transmission waiting time using a random number. The determined initial transmission waiting time for high priority is set in the initial transmission back-off timer for high priority.
When the initial transmission waiting time has expired, the MAC control unit 404 extracts the radio frame from the initial transmission queue and outputs the radio frame to the radio interface control unit 406.

The radio interface control unit 406 performs CCA before transmitting the radio frame generated by the MAC control unit 404. As a result of the CCA, if the initial transmission of the radio frame is not possible, the radio interface control unit 406 returns the radio frame to the MAC control unit 404.
The MAC control unit 404 stores the radio frame that could not be transmitted for the first time by the CCA in a retransmission credit queue for each priority level, determines a retransmission waiting time using a random number, and determines the determined retransmission time. Set the transmission wait time to the retransmission backoff timer.
The operation after the retransmission waiting time expires is the same as the operation after the initial transmission waiting time expires. When the radio frame cannot be retransmitted by the CCA, the MAC control unit 404 determines a retransmission waiting time for further retransmission, and sets the determined retransmission waiting time in the retransmission backoff timer.

Even if the wireless frame can be transmitted for the first time, but the response to the wireless frame cannot be received from the notification destination device, the wireless interface control unit 406 also transmits the wireless frame that has not received the response to the MAC control unit. Return to 404.
The MAC control unit 404 stores the radio frame for which the response has not been received in a retransmission credit queue for each priority, determines a retransmission waiting time using a random number, and re-transmits the determined retransmission waiting time. Set to transmission backoff timer.
The operation after the retransmission waiting time expires is the same as the operation after the initial transmission waiting time expires. When the radio frame cannot be retransmitted by the CCA, the MAC control unit 404 determines a retransmission waiting time for further retransmission, and sets the determined retransmission waiting time in the retransmission backoff timer.
In addition, when the wireless frame can be retransmitted, but the response to the wireless frame cannot be received from the notification destination device, the MAC control unit 404 also waits for retransmission for further retransmission. And the determined retransmission waiting time is set in the retransmission back-off timer.
Thereafter, each time retransmission fails, the above operation is repeated until the upper limit number of retransmissions is reached.

  Next, an operation example of the wireless communication apparatus 100 according to the present embodiment will be described with reference to the flowcharts of FIGS. Note that the flowcharts of FIGS. 5 and 6 show an operation example of the wireless communication apparatus 100 compliant with IEEE 802.15.4. Note that the operation procedures shown in FIGS. 5 and 6 can be applied to the wireless communication apparatus 100 conforming to IEEE 802.15.4, and can be widely applied to the wireless communication apparatus 100 compatible with CSMA / CA.

  When a transmission event occurs (step S501), that is, when the sensor interface control unit 401 receives a sensor signal, the application determination unit 402 determines whether the transmission event is an emergency event (step S502). . That is, the application determination unit 402 determines whether or not the phenomenon notified by the sensor signal received by the sensor interface control unit 401 is an emergency notification target.

If the transmission event is not an emergency event, the MAC control unit 404 generates a radio frame including the sensor signal, stores the radio frame in a queue for initial transmission of medium priority or low priority, and waits for initial transmission. Is set as a back-off timer (step S503).
Since it is the first transmission, the MAC control unit 404 determines the initial transmission waiting time by a random number from the first time width, and sets the determined initial transmission waiting time in the back-off timer.
The first time width is composed of i slots (i is an integer equal to or greater than 3) having a predetermined slot width, and the MAC control unit 404 selects one of the i slots from a random number. The time corresponding to the selected slot is determined as the initial transmission waiting time.
For example, if the slot width is 1 millisecond and i is 100, the first time width is 100 milliseconds. Then, when the 70th slot is selected by a random number, the MAC control unit 404 sets 70 milliseconds as the initial transmission waiting time in the back-off timer.

  When the back-off timer expires, the radio interface control unit 406 performs CCA (step S504) and confirms the radio status in the radio communication line (step S505).

If the wireless interface control unit 406 determines that the wireless frame can be transmitted as a result of the CCA, the wireless interface control unit 406 transmits the wireless frame to the notification destination device (step S507).
Then, the MAC control unit 404 returns the back-off count described later to an initial value (step S508).

  On the other hand, in step S505, if the surrounding wireless environment is congested as a result of the CCA and the wireless interface control unit 406 determines that the wireless frame cannot be transmitted (retransmission is necessary), the MAC control unit 404 The off count is incremented by 1 (step S515). The number of backoffs is the number of retransmissions by CCA.

  Next, the MAC control unit 404 determines whether or not the number of back-offs has reached the upper limit number (step S516). If the back-off number has reached the upper limit number, the MAC control unit 404 determines that the transmission has failed. Determination is made and the number of back-offs is returned to the initial value (step S508).

On the other hand, if the back-off count has not reached the upper limit count, the radio frame is returned to the MAC control unit 404, and the MAC control unit 404 stores the radio frame in a retransmission priority queue of medium priority or low priority. The retransmission waiting time is set in the back-off timer (S503).
Since it is retransmission, the MAC control unit 404 determines a retransmission waiting time from a second time width shorter than the first time width by a random number, and sets the determined retransmission waiting time in the back-off timer. To do.
More specifically, the second time width is composed of j slots (j is an integer equal to or larger than 2 and less than i) having a predetermined slot width, and the MAC control unit 404 uses j random numbers. Any slot is selected from among the slots, and a time corresponding to the selected slot is determined as a retransmission waiting time.
For example, if the slot width is 1 millisecond and j is 50, the second time width is 50 milliseconds. Then, when the 30th slot is selected by a random number, the MAC control unit 404 sets 30 milliseconds as the initial transmission waiting time in the back-off timer.
Since the processing after step S504 is as described above, a description thereof will be omitted.

If it is determined in step S502 that the transmission event is an emergency event, the MAC control unit 404 generates a wireless frame including the sensor signal, stores the wireless frame in a high-priority initial transmission queue, and performs initial transmission. A back-off timer is set for the waiting time (step S509).
Since it is the first transmission, the MAC control unit 404 determines the initial transmission waiting time by a random number from the first time width, and sets the determined initial transmission waiting time in the back-off timer.
Note that the method for determining the initial transmission wait time in step S509 is the same as the method for determining the initial transmission wait time described in step S503. However, the MAC control unit 404 may make the first time width of the high-priority wireless frame shorter than the first time width of the low-priority wireless frame. As described above, when the first time width of the low-priority wireless frame is 100 milliseconds, the MAC control unit 404 sets the first time width of the high-priority wireless frame to 60 milliseconds, for example. Seconds may be used.

  When the back-off timer expires, the radio interface control unit 406 performs CCA (step S510) and confirms the radio status in the radio communication line (step S511).

If the wireless interface control unit 406 determines that the wireless frame can be transmitted as a result of the CCA, the wireless interface control unit 406 transmits the wireless frame to the notification destination device (step S513).
Then, the MAC control unit 404 returns the number of backoffs to the initial value (step S514).

  On the other hand, if it is determined in step S511 that the radio interface control unit 406 cannot transmit a radio frame (retransmission is necessary) as a result of CCA, the MAC control unit 404 increments the number of backoffs by 1 (step S517).

  Next, the MAC control unit 404 determines whether or not the number of back-offs has reached the upper limit number (step S518). If the back-off number has reached the upper limit number, the MAC control unit 404 determines that the transmission has failed. Determination is made and the number of back-offs is returned to the initial value (step S514).

On the other hand, if the number of backoffs has not reached the upper limit, the radio frame is returned to the MAC control unit 404, and the MAC control unit 404 stores the radio frame in a high-priority retransmission credit queue and waits for retransmission. Time is set in the back-off timer (S509).
Note that the retransmission waiting time determination method in step S509 is the same as the retransmission waiting time determination method described in step S503. However, the MAC control unit 404 may make the second time width of the high-priority wireless frame shorter than the second time width of the low-priority wireless frame. As described above, when the second time width of the low-priority wireless frame is 50 milliseconds, the MAC control unit 404 sets the second time width of the high-priority wireless frame to, for example, 30 milliseconds. Seconds may be used.
Since the process after step S510 is as described above, the description thereof is omitted.

Next, an operation example of the wireless communication apparatus 100 when a response from the notification destination apparatus cannot be received will be described with reference to the flowcharts of FIGS. 7 and 8.
In the flowcharts of FIG. 5 and FIG. 6, the example in which the retransmission waiting time is set in the back-off timer because a radio frame cannot be generated by the CCA has been described. The flowcharts of FIGS. 7 and 8 describe an example in which the retransmission waiting time is set in the back-off timer because the CCA has succeeded and the radio frame has been transmitted, but no response has been received from the notification destination apparatus.

  In FIG. 7, S601 to S603 are the same as S501 to S503 in FIG.

When the back-off timer expires, the radio interface control unit 406 performs CCA, and the radio interface control unit 406 determines that transmission of a radio frame is possible (step S604).
Then, the wireless interface control unit 406 transmits a wireless frame to the notification destination device (step S605).

The wireless interface control unit 406 determines whether a response has been received from the notification destination apparatus within a predetermined time from the transmission of the wireless frame (step S606). The response from the notification destination device is, for example, MAC Ack.
If the wireless interface control unit 406 has received a response within a certain period from the transmission of the wireless frame, the MAC control unit 404 returns the number of retransmissions described later to an initial value (step S608).

  On the other hand, in step S606, when the wireless interface control unit 406 does not receive a response within a certain period from the transmission of the wireless frame, the MAC control unit 404 increments the number of retransmissions by 1 (step S607). The number of retransmissions is the number of retransmissions due to a failure to receive a response.

Then, the radio frame is returned to the MAC control unit 404, and the MAC control unit 404 stores the radio frame in a medium-priority or low-priority retransmission credit queue and sets a retransmission waiting time in a back-off timer ( S603).
Note that the retransmission waiting time determination method here is the same as the retransmission waiting time determination method described in step S503 in FIG.
Since the processing after step S604 is as described above, the description thereof is omitted.

Step S609 is the same as S509 in FIG.
Steps S610 to S614 are the same as S604 to S608 in FIG.
After the number of retransmissions is incremented by 1 in step S613, the radio frame is returned to the MAC control unit 404. The MAC control unit 404 stores the radio frame in a high-priority retransmission credit queue and backs off the retransmission waiting time. The timer is set (S609).
Note that the retransmission waiting time determination method here is the same as the retransmission waiting time determination method described in step S503 in FIG.
Although not shown in FIGS. 7 and 8, the MAC control unit 404 compares the number of retransmissions with the upper limit number, and when the number of retransmissions reaches the upper limit number, the retransmission of the radio frame is performed. May be canceled.

In this embodiment, in order to facilitate understanding, an operation procedure in the case of retransmission by CCA (FIGS. 5 and 6) and an operation procedure in the case of retransmission due to failure in receiving a response (FIGS. 7 and 7) Although the description is divided into FIG. 8, the radio communication device 100 operates in the case of retransmission by CCA (FIG. 5 and FIG. 6) and the operation procedure in the case of retransmission due to failure in receiving a response ( The operation combining FIG. 7 and FIG. 8) is performed.
That is, radio communication apparatus 100 performs step S606 after step S507 in FIG. 5, and if transmission fails, sets retransmission retransmission waiting time in the backoff timer in step S603 after step S607.
Similarly, radio communication apparatus 100 performs step S612 in FIG. 8 after step S513 in FIG. 6, and if transmission fails, sets retransmission retransmission waiting time in the backoff timer in step S609 after step S613. To do.

Next, the operation of the MAC control unit 404 according to the present embodiment will be described in detail with reference to FIG.
In the following, the operation of the MAC control unit 404 when the CCA is successful and a radio frame is transmitted to the notification destination device but a response from the notification destination device cannot be received will be described.

As shown in FIG. 9, the MAC control unit 404 manages a transmission queue 701, a high priority initial transmission queue 704, a high priority retransmission queue 702, a normal priority initial transmission queue 708, and a normal priority retransmission queue 706. To do.
Further, the MAC control unit 404 includes a high priority initial transmission backoff timer 705, a high priority retransmission backoff timer 703, a normal priority initial transmission backoff timer 709, and a normal priority retransmission backoff timer. 707 is managed.

First, the MAC control unit 404 generates a radio frame including the sensor signal, and stores the generated radio frame in the transmission queue 701. Then, if the wireless frame is an emergency notification target, the MAC control unit 404 stores the wireless frame in the high priority first transmission queue 704. On the other hand, if the wireless frame is a target of normal application notification, the MAC control unit 404 stores the wireless frame in the normal priority initial transmission queue 708.
In the initial transmission of the high priority wireless frame, the MAC control unit 404 sets the initial transmission waiting time in the high priority initial transmission backoff timer 705. When the high priority initial transmission back-off timer 705 expires, the MAC control unit 404 extracts the radio frame from the high priority initial transmission queue 704 and outputs the radio frame to the radio interface control unit 406. In the initial transmission of the normal priority radio frame, the MAC control unit 404 sets the initial transmission waiting time in the normal priority initial transmission back-off timer 709. When the normal priority initial transmission back-off timer 709 expires, the MAC control unit 404 extracts the radio frame from the normal priority initial transmission queue 708 and outputs the radio frame to the radio interface control unit 406.
When the CCA is successful and the radio frame is transmitted from the radio interface control unit 406, but there is no response from the notification destination device, the radio frame is returned from the radio interface control unit 406 to the MAC control unit 404, and the transmission queue 701 is transmitted. Stored in
The MAC control unit 404 stores the radio frame from the transmission queue 701 to the high priority retransmission queue 702 if the radio frame is an emergency notification target. On the other hand, if the radio frame is the target of normal application notification, the MAC control unit 404 stores the radio frame from the transmission queue 701 to the normal priority retransmission queue 706.
In retransmission of a high priority radio frame, the MAC control unit 404 sets a retransmission waiting time in the high priority retransmission backoff timer 703. When the high-priority retransmission back-off timer 703 expires, the MAC control unit 404 extracts the radio frame from the high-priority retransmission queue 702 and outputs the radio frame to the radio interface control unit 406. In the retransmission of the normal priority radio frame, the MAC control unit 404 sets a retransmission waiting time in the normal priority retransmission back-off timer 707. When the normal priority retransmission back-off timer 707 expires, the MAC control unit 404 extracts the radio frame from the normal priority retransmission queue 706 and outputs the radio frame to the radio interface control unit 406.

In FIG. 9, the first transmission queue and the retransmission credit queue are separated, but only one queue is used if the first transmission radio frame and the retransmission radio frame can be distinguished. You may make it do.
Further, in FIG. 9, two examples of high priority and normal priority are shown as the priority hierarchy, but the priority hierarchy is not limited to two.

  Next, an operation example of the MAC control unit 404 when the CCA fails will be described with reference to FIG.

As shown in FIG. 10, the MAC control unit 404 manages a transmission queue 801, a high priority initial transmission queue 804, a high priority retransmission queue 802, a normal priority initial transmission queue 808, and a normal priority retransmission queue 806. To do.
Further, the MAC control unit 404 includes a high priority initial transmission back-off timer 805, a high priority re-CCA back-off timer 803, a normal priority initial transmission back-off timer 809, and a normal priority re-CCA back-off timer. 807 is managed.
The transmission queue 801 is the same as the transmission queue 701 in FIG. The high priority initial transmission queue 804 is the same as the high priority initial transmission queue 704 of FIG. The high priority retransmission queue 802 is the same as the high priority retransmission queue 702 of FIG. The normal priority retransmission queue 806 is the same as the normal priority retransmission queue 706 of FIG. The normal priority initial transmission queue 808 is the same as the normal priority initial transmission queue 708 of FIG. The high priority initial transmission backoff timer 805 is the same as the high priority initial transmission backoff timer 705 of FIG. The high priority retransmission CCA back-off timer 803 is the same as the high priority retransmission back-off timer 703 of FIG. The normal priority initial transmission backoff timer 809 is the same as the normal priority initial transmission backoff timer 709 of FIG. The normal priority retransmission CCA back-off timer 807 is the same as the normal priority retransmission back-off timer 707 of FIG.

First, the MAC control unit 404 generates a radio frame including the sensor signal, and stores the generated radio frame in the transmission queue 801. Then, the MAC control unit 404 stores the radio frame in the high priority first transmission queue 804 if the radio frame is a target of emergency notification. On the other hand, if the wireless frame is the target of normal application notification, the MAC control unit 404 stores the wireless frame in the normal priority first transmission queue 808.
In the initial transmission of the high priority radio frame, the MAC control unit 404 sets the initial transmission waiting time in the high priority initial transmission backoff timer 805. When the high priority initial transmission back-off timer 805 expires, the MAC control unit 404 extracts the radio frame from the high priority initial transmission queue 804 and outputs the radio frame to the radio interface control unit 406. In the initial transmission of the normal priority radio frame, the MAC control unit 404 sets the initial transmission waiting time in the normal priority initial transmission back-off timer 809. When the normal priority initial transmission back-off timer 809 expires, the MAC control unit 404 extracts the radio frame from the normal priority initial transmission queue 808 and outputs the radio frame to the radio interface control unit 406.
When the CCA fails, the wireless frame is returned from the wireless interface control unit 406 to the MAC control unit 404 and stored in the transmission queue 801.
The MAC control unit 404 stores the radio frame from the transmission queue 801 to the high priority retransmission queue 802 if the radio frame is an emergency notification target. On the other hand, if the wireless frame is the target of normal application notification, the MAC control unit 404 stores the wireless frame from the transmission queue 801 into the normal priority retransmission queue 806.
In retransmission of a high priority radio frame, the MAC control unit 404 sets a retransmission waiting time in the high priority re-CCA backoff timer 803. When the high priority re-CCA back-off timer 803 expires, the MAC control unit 404 extracts the radio frame from the high priority retransmission queue 802 and outputs the radio frame to the radio interface control unit 406. In the retransmission of the normal priority radio frame, the MAC control unit 404 sets a retransmission waiting time in the normal priority re-CCA back-off timer 807. When the normal priority re-CCA back-off timer 807 expires, the MAC control unit 404 extracts the radio frame from the normal priority retransmission queue 806 and outputs the radio frame to the radio interface control unit 406.

  FIG. 11 shows an example of the initial transmission waiting time and an example of the retransmission waiting time set when the CCA fails.

In FIG. 11, the wireless communication apparatus 101 determines an initial transmission waiting time 901 from the first time width using a random number. Then, after the initial transmission waiting time 901 expires, the wireless communication apparatus 101 performs CCA, succeeds in CCA, and transmits a wireless frame.
The wireless communication apparatus 102 determines the initial transmission waiting time 902 from the first time width using a random number. Since the initial transmission waiting time is determined by a random number, the initial transmission waiting time 901 of the wireless communication apparatus 101 and the initial transmission waiting time 902 of the wireless communication apparatus 102 are different.
After the initial transmission waiting time 902 expires, the wireless communication device 102 performs CCA and fails in CCA. For this reason, the wireless communication apparatus 102 determines the retransmission waiting time 903 by using a random number from the second time width. After the retransmission waiting time 903 expires, CCA is performed and the CCA fails. For this reason, the wireless communication apparatus 102 further determines a retransmission waiting time 904 using a random number from the second time width. Since the retransmission waiting time is determined by a random number, the retransmission waiting time 903 and the retransmission waiting time 904 are different. In the example of FIG. 11, the wireless communication device 102 succeeds in CCA after expiration of the retransmission waiting time 904 and transmits a wireless frame to the notification destination device.

  FIG. 12 shows an example of an initial transmission waiting time and an example of a retransmission waiting time set when reception of a response fails.

In FIG. 12, the wireless communication apparatus 101 determines an initial transmission waiting time 1001 using a random number from the first time width. Then, after the initial transmission waiting time 1001 expires, the wireless communication device 101 performs CCA, succeeds in CCA, and transmits a wireless frame. However, the wireless communication apparatus 101 cannot receive a response from the GW apparatus 200 that is a notification destination apparatus.
For this reason, the wireless communication apparatus 101 determines the retransmission waiting time 1002 using a random number from the second time width. After the retransmission waiting time 1002 expires, CCA is performed, the CCA is successful, and a radio frame is transmitted. However, the wireless communication apparatus 101 cannot receive a response from the GW apparatus 200. For this reason, the wireless communication apparatus 101 further determines a retransmission waiting time 1003 by a random number from the second time width. Since the retransmission waiting time is determined by a random number, the retransmission waiting time 1002 and the retransmission waiting time 1003 are different. In the example of FIG. 12, the wireless communication device 101 succeeds in CCA after expiration of the retransmission waiting time 1003, transmits a wireless frame to the notification destination device, and receives a response from the GW device 200.

*** Explanation of the effect of the embodiment ***
According to the present embodiment, since the retransmission waiting time is selected from the second time width shorter than the first time width, even if the initial transmission fails, there is a possibility that retransmission will be performed early. Can be increased.
Therefore, even in a situation where emergency notifications can occur simultaneously in a plurality of wireless communication devices, transmission of emergency notifications from all the wireless communication devices can be completed in an expected request time.

Embodiment 2. FIG.
In the first embodiment, the example in which the MAC control unit 404 determines the retransmission waiting time based on the fixed second time width has been described.
Alternatively, the MAC control unit 404 may determine the retransmission waiting time based on the variable second time width.
For example, the MAC control unit 404 may change the length of the second time width according to the communication status in the wireless communication line on which the wireless interface control unit 406 performs retransmission.
Specifically, the MAC control unit 404 increases the second time width as the communication amount on the wireless communication line increases, that is, as the wireless communication line is congested.
However, the MAC control unit 404 prevents the second time width from exceeding the first time width.

  The present embodiment is the same as the first embodiment except that the second time width is variable. That is, the hardware configuration and functional configuration of radio communication apparatus 100 and the operation procedure of radio communication apparatus 100 are as described in the first embodiment.

Embodiment 3 FIG.
In the first embodiment, the first time width is configured by i slots having a predetermined slot width, and the second time width is configured by j slots (j <i) having the same slot width. Explained.
Instead, the first time width is composed of n slots (n is an integer of 2 or more) of the first slot width, and the second time width is shorter than the first slot width. It may be composed of n slots having a slot width of 2.
FIG. 13 shows an example of the first time width and the second time width according to the present embodiment.
In FIG. 13, n = 10. That is, each of the first time width and the second time width includes 10 slots.
However, the slot width (second slot width) of the slot 1302 constituting the second time width is shorter than the slot width (first slot width) of the slot 1301 constituting the first time width.
For this reason, the second time width is shorter than the first time width.
According to the present embodiment, by making the slot width of the second time width shorter than the slot width of the first time width, the probability of failure in CCA upon retransmission of the radio frame (other radio communication (Probability of colliding with the device 100) can be reduced.
FIG. 13 shows the second time width that is a premise of the retransmission waiting time when the CCA fails, but the second time width that is a premise of the retransmission waiting time when the response from the notification destination apparatus fails to be received. Similarly to FIG. 13, the time width may be constituted by slots having a second slot width shorter than the first slot width.

  The present embodiment is the same as the first embodiment except that the configurations of the first time width and the second time width are different. That is, the hardware configuration and functional configuration of radio communication apparatus 100 and the operation procedure of radio communication apparatus 100 are as described in the first embodiment.

Embodiment 4 FIG.
In the first embodiment, as shown in FIG. 9, a retransmission credit back-off timer (high-priority retransmission back-off timer 703, normal-priority retransmission back-off timer) for each of high priority and normal priority. 707), but as shown in FIG. 14, with normal priority, the retransmission credit back-off timer (normal priority retransmission back-off timer 707) may be omitted.
Also in the configuration of FIG. 13, the normal priority retransmission credit back-off timer (normal priority re-CCA back-off timer 807) may be omitted.

In the first embodiment, the second time width is shorter than the first time width for all priorities, but the second time width is the first time width for the lowest priority. It may be made longer. That is, at the lowest priority, the probability that the retransmission waiting time becomes longer than the initial transmission waiting time may be increased.
By doing so, it is possible to reduce congestion in wireless communication.

  Although the wireless communication device 100 has been described in the first to fourth embodiments, the operation of the wireless communication device 100 described in the first to fourth embodiments can be applied to a communication device that performs wired communication.

As mentioned above, although embodiment of this invention was described, you may implement in combination of 2 or more among these embodiment.
Alternatively, one of these embodiments may be partially implemented.
Alternatively, two or more of these embodiments may be partially combined.
In addition, this invention is not limited to these embodiment, A various change is possible as needed.

*** Explanation of hardware configuration ***
Finally, a supplementary description of the hardware configuration of the wireless communication apparatus 100 will be given.
The ROM 305 stores an OS (Operating System) in addition to programs for realizing the application determination unit 402, the priority control unit 403, and the MAC control unit 404.
At least a part of the OS is executed by the processor 304.
When the processor 304 executes the OS, task management, memory management, file management, communication control, and the like are performed.
In addition, information, data, signal values, and variable values indicating the processing results of the application determination unit 402, the priority control unit 403, and the MAC control unit 404 are stored in the RAM 306, the wireless MAC processing processor 302 or the processor 304 in the register 304 or cache. Stored in memory.
A program that realizes the application determination unit 402, the priority control unit 403, and the MAC control unit 404 is stored in a portable storage medium such as a magnetic disk, a flexible disk, an optical disk, a compact disk, a Blu-ray (registered trademark) disk, or a DVD. May be.

Further, the “unit” of the application determination unit 402, the priority control unit 403, and the MAC control unit 404 may be read as “circuit”, “process”, “procedure”, or “processing”.
The wireless communication apparatus 100 may be realized by an electronic circuit such as a logic IC (Integrated Circuit), a GA (Gate Array), an ASIC (Application Specific Integrated Circuit), or an FPGA (Field-Programmable Gate Array).
In this case, the application determination unit 402, the priority control unit 403, and the MAC control unit 404 are each realized as part of an electronic circuit.
The processor and the electronic circuit are also collectively referred to as a processing circuit.

  DESCRIPTION OF SYMBOLS 100 Wireless communication apparatus, 200 GW apparatus, 301 Wireless interface, 302 Wireless MAC processing processor, 303 Sensor interface, 304 Processor, 305 ROM, 306 RAM, 401 Sensor interface control part, 402 Application determination part, 403 Priority control part, 404 MAC Control unit, 405 Data management unit, 406 Wireless interface control unit, 701 Transmission queue, 702 High priority retransmission queue, 703 High priority retransmission backoff timer, 704 High priority initial transmission queue, 705 High priority Initial transmission backoff timer, 706 Normal priority retransmission queue, 707 Normal priority retransmission backoff timer, 708 Normal priority initial transmission queue, 709 Normal priority initial transmission backoff timer, 801 Transmission queue 802 High priority retransmission queue 803 High priority re-CCA back-off timer 804 High priority initial transmission queue 805 High priority initial transmission back-off timer 806 Normal priority retransmission queue 807 Normal priority Re-CCA back-off timer for regular use, 808 normal priority first transmission queue, 809 normal priority first transmission back-off timer.

Claims (11)

An initial transmission waiting time determination unit for determining an initial transmission waiting time, which is a waiting time before performing the first transmission of data, using a random number from the first time width;
When the first transmission fails, a retransmission waiting time that is a waiting time before performing data retransmission is determined from the second time width shorter than the first time width using the random number. A communication apparatus having a retransmission waiting time determining unit. The retransmission waiting time determining unit
The retransmission waiting time is determined in at least one of a case where the initial transmission could not be performed and a case where the initial transmission could be performed but a response to the initial transmission could not be received. Item 4. The communication device according to Item 1. The retransmission waiting time determining unit
The communication device according to claim 1, wherein when the retransmission fails, a waiting time before further retransmission is determined using the random number from the second time width. The retransmission waiting time determining unit
Before performing the further retransmission in at least one of the case where the retransmission could not be performed and the case where the retransmission could be performed but a response to the retransmission could not be received The communication device according to claim 3, wherein the waiting time is determined. The retransmission waiting time determining unit
The communication apparatus according to claim 1, wherein the length of the second time width is changed in accordance with a communication state in a communication line on which the communication apparatus performs the retransmission. The retransmission waiting time determining unit
The communication apparatus according to claim 5, wherein the second time width is increased as the communication amount on the communication line increases. The initial transmission waiting time determining unit
The initial transmission waiting time is determined using the random number from the first time width, each of which is composed of n slots (n is an integer of 2 or more) each having a first slot width,
The retransmission waiting time determining unit
The retransmission waiting time is determined using the random number from the second time width composed of n slots each having a second slot width shorter than the first slot width. The communication apparatus according to 1. The initial transmission waiting time determining unit
For each data priority, the initial transmission waiting time is determined,
The retransmission waiting time determining unit
The communication apparatus according to claim 1, wherein the retransmission waiting time is determined for each priority.   The communication device according to claim 1, wherein the communication device is a wireless communication device. The computer determines a first transmission waiting time, which is a waiting time before the first transmission of data, using a random number from the first time width,
When the computer fails in the initial transmission, a retransmission waiting time, which is a waiting time before performing data retransmission, is set to the random number from a second time width shorter than the first time width. Communication method to be determined using. An initial transmission waiting time determination process for determining an initial transmission waiting time, which is a waiting time before the first transmission of data, using a random number from the first time width;
When the first transmission fails, a retransmission waiting time that is a waiting time before performing data retransmission is determined from the second time width shorter than the first time width using the random number. A communication program for causing a computer to execute a retransmission waiting time determination process.

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